User interface devices often include key panels that can be used to make selections, input data, and so forth. In harsh environments, key panels may be subject to water and/or debris (e.g., dust, sand, etc.) that can cause damage to underlying circuitry or components if the water and/or debris enters an airgap that typically exists between the bezel and buttons (sometimes referred to as “keys”) of the key panel.
To keep out moisture and debris, a harsh environment key panel may include a flexible rubber substrate placed over the buttons, or placed over switches on a printed board below the buttons. Either approach requires multiple parts to be manufactured and assembled. Tolerances must be tightly controlled to ensure product integrity and survivability. Furthermore, some of the tactile feedback from the switches can be lost through the cushioning effect of the rubber substrate, resulting in a lower quality user experience.
Another approach for keeping out moisture and debris, is to use membrane type switches (instead of mechanical switches) for the key panel. Membrane type switches are typically low profile, lightweight, and cheap to manufacture in large quantities. However, membrane type switches generally do not have good tactile feedback when actuated. Durability of the switch membranes can also become a concern in high usage cases.
An avionic key panel typically includes a small amount of gasket material around each button to keep dust and other debris out of the key panel assembly. However, this gasket material does little to keep out moisture, especially if a button is pressed during exposure or if the key panel itself has continuous exposure to water or other moisture. There have been some cases of avionic key panels failing due to extreme exposure to sand or dust. For example, the switches located below the buttons can become jammed by debris and stop actuating as a result.
Several approaches for making harsh environment key panel and bezel structures exist. However, as demonstrated above, the existing harsh environment key panels have various structural limitations or process difficulties associated with their manufacture. Consequently, there is a need for robust and low cost key panel and bezel structures that work well to keep moisture and debris from reaching printed boards, switches, and other underlying key panel circuitry and/or components.